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[Bug target/47000] Major performance regression in parallel SSE2 impl of SHA256 hash algorithm
- From: "steven at gcc dot gnu.org" <gcc-bugzilla at gcc dot gnu dot org>
- To: gcc-bugs at gcc dot gnu dot org
- Date: Sat, 18 Dec 2010 12:39:32 +0000
- Subject: [Bug target/47000] Major performance regression in parallel SSE2 impl of SHA256 hash algorithm
- Auto-submitted: auto-generated
- References: <bug-47000-4@http.gcc.gnu.org/bugzilla/>
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=47000
Steven Bosscher <steven at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|UNCONFIRMED |NEW
Last reconfirmed| |2010.12.18 12:39:26
Ever Confirmed|0 |1
--- Comment #3 from Steven Bosscher <steven at gcc dot gnu.org> 2010-12-18 12:39:26 UTC ---
Compiled like so:
$ gcc-4.4.2 -S -O2 sha256_4way.i -o sha256_4way-44.s
$ gcc-4.5.0 -S -O2 sha256_4way.i -o sha256_4way-45.s
$ grep -c call *.s
sha256_4way-44.s:0
sha256_4way-45.s:484
$ grep call *.s|head
sha256_4way-45.s: call ROTR
sha256_4way-45.s: call ROTR
sha256_4way-45.s: call ROTR
sha256_4way-45.s: call ROTR
sha256_4way-45.s: call ROTR
sha256_4way-45.s: call ROTR
sha256_4way-45.s: call ROTR
sha256_4way-45.s: call ROTR
sha256_4way-45.s: call ROTR
sha256_4way-45.s: call ROTR
$
ROTR should have been inlined:
static inline __m128i ROTR(__m128i x, const int n) {
return _mm_srli_epi32(x, n) | _mm_slli_epi32(x, 32 - n);
}
This probably explains the slowdown.